Cultivators to work the soil have been known for many years. From earliest times, farmers have cultivated the soil in an effort to prevent weed and grass growth that compete with crop growth for moisture and nutrients. Animal drawn single row cultivators have been in use for thousands of years. Multi-row cultivators came into more widespread use with the advent of the mechanized age. Today, tractors are used to pull multi-row cultivators through fields. To date, the cultivators in use have all had one or more disadvantages which prevent optimum cultivation and plant growth.
In today's mechanized farming environment, seed beds are prepared and seeds planted in the beds by tractor drawn implements. Generally, one or more rows of bed preparers/planters are drawn through a field. In a single operation, they open a bed, plant the seed, and cover the planted seed. One such apparatus is described in detail in U.S. Pat. No. 4,187,916, issued Feb. 12, 1980, to J. Harden et al. Another such "single pass" planter is shown in U.S. Pat. No. 4,601,248, issued Jul. 22, 1986, to E. Beasley. Planters of the type shown in the Harden '916 and Beasley '248 patents should not be confused with cultivators, however, which are used to cultivate the soil in an already planted field.
As tractors and equipment travel over the field, they pack down the earth between the seed bed rows. This results in the creation of densely compacted soil at and several inches below the earth surface. The compacted soil inhibits plant growth; plant roots are restricted from penetrating the condensed, packed earth between the plant rows. The plant roots are therefore unable to gain full access to and the benefit of the surface and sub-surface areas that could otherwise provide water and other nutrients to the plant roots.
Known cultivators have been used almost exclusively to try to control the growth of weeds and grasses, which are the "enemy" of crops. Conventional cultivators are designed to plow between crop rows (in the "row middles") at very shallow depths to kill weeds and grass. They do this by cutting the weed and grass plants loose from their roots just below the earth's surface. Existing cultivators only loosen up the top 1"-2" of soil. With sun beating down on the field, this top part of the soil becomes the hottest part of the soil. Surface temperatures can rise to 130.degree.-140.degree. F. This causes the surface soil to dry out quickly and bake any plant roots growing near the surface.
In conventional farming, using known cultivators, the row middles, even after cultivation, are so tightly packed that rain water cannot penetrate the soil to a depth at which roots could be expected to grow. Rainwater therefore merely runs off the field into the drains and rivers, carrying with it valuable nutrients, such as fertilizers and pesticides. This not only robs the crops of needed nutrients, but it also adds to environmental problems and creates additional pollution of the creek and river waters.
Known cultivators generally have "sweeps" or wing-like members which are dragged by a tractor or the like through the ground just below the surface of the row middle. Sweep assemblies are well known in the agricultural industry. Kelly Manufacturing Corporation, of Tifton, Ga., manufactures a line of cultivators with sweep assemblies.
Known cultivators used in "conventional farming" environments (in which the remains of a winter cover crop or a previous year's crop residue have been cleared from the field before the current planting season, such remains being generally known in the agricultural industry as "trash") may have three to five or more sweeps for each row middle. Conventional fanning cultivators will also usually have one or two coulters for the entire assembly for stability.
Known cultivators used in "no-till" farming (in which the trash is left undisturbed in the field) consist of two (or three) elements for each row: a coulter and a single large sweep (and a gauge wheel, which controls the depth of the sweep). Each sweep will generally have a span of 28"-32". It has been found in practice that it is very difficult to get such a large sweep to go into the ground in the first place and then keep it in the ground at the desired depth for cultivating the soil.
Known cultivators rely on the weight of the cultivator unit (alone or with the weight of the tool bar added) to provide the force necessary to drive the sweeps into the ground. This is a problem when the ground consists of hard earth or the density of the soil is uneven (having randomly located hard and soft spots). The sweeps will often pop out of the ground when they hit a hard spot. Or they will drive deeply into the softer ground, going under the weed and grass plants, thereby missing them entirely.
When cultivating fields planted with crops like corn, soybeans, or cotton, the cultivator is set to throw dirt onto the crop row itself at the base of the crop. This is done to cover up the weeds and grasses that are growing in the crop row and which therefore cannot be cut without also cutting the crop plants. However, when working in fields planted with peanuts, for example, the cultivator must be set to keep from throwing dirt onto the crop row.
As will be described in detail below, the present invention overcomes the deficiencies of and problems associated with the conventional technology noted above.